- From: Manuel Strehl <svg@manuel-strehl.de>
- Date: Tue, 2 Sep 2008 08:44:11 +0200 (CEST)
- To: www-svg@w3.org

Hi, > fyi - there was just a paper and presentation at the SVG Open on the > topic of achieving 3D effects in SVG at the SVG Open 2008 in > Nuremberg. thanks, I know. Actually I talked to Anthony and told him, that I'll send my proposal via this list. However, I'd like to ask everyone else interested in pseudo-3D to sync efforts with Jun and Anthony. For my formula from yesterday: I'll promise for future formulas to sleep one night before posting them. Remarks: * It will only be valid for objects that are star-shaped with respect to P(x,y) (I mentioned something like that) * error: Of course, the displacements have to be weighted with the distance from the original bounding box to give useful results, e.g., for trapezoids: P(x,y) -> P(x',y'), with x' = x + (deviation_left*(1 - x_rel/width) - deviation_right*(x_rel/width)), y' = y + (deviation_top*(1 - y_rel/height) - deviation_bottom*(y_rel/height)), where y_rel = 0 for a point lying on the top line of the original bounding box, y_rel = height for a point on the bottom line of the bb. Something like that... Best, Manuel > > > https://www.svgopen.org/2008/papers/86-Achieving_3D_Effects_with_SVG/ > > The authors, Jun Fujisawa and Anthony Grasso, intend to write a spec > proposal for a separate module for perspective transformations in SVG. > You could participate in this effort as part of the SVG interest group > if you want. > > Andreas > > Manuel Strehl wrote: >> Hi, >> >> formulas: Sorry, I don't do this usually, so it will not be quite >> usable. In fact it's just a thought. I don't know, if it would display >> correctly and in the sense intended. >> >> * expand/contract the referenced path to meet width and height of the >> element's bounding box >> * P(x,y) an undistorted point of the element >> * A displayed point P'(x', y') will depend on the deviations of the >> bounding box from the border of the referenced path >> * If the two deviations, say, at the top and at the bottom are equal, y' >> = y, same for left/right and the x axis >> * otherwise x' = x + (deviation_left - deviation_right), y' = y + >> (deviation_top - deviation_bottom) >> >> It is quite probable, that one has to take the x deviation for y into >> account, since there can be dependencies for complex paths (leading to >> some kind of convergence calculation). That's not respected by the above >> instructions. Also for twisted paths, spirals and so on, I guess you'll >> have a hard time to define the deviation clearly. >> >> On implementor's side in the linear case (see below) it should be >> possible to look at how, e.g., GIMP is doing it for pixels or, >> for a simple example in SVG (only trapezoids), Inkscape's plugin >> "perspective.py", usually living at /usr/share/inkscape/extensions or >> %ProgramFiles%\Inkscape\share\extensions. It does it with a simple >> python based geometry library (~250 lines code). >> >> The path structure would not neccessarily be conserved (the "non-linear >> case"). Consider some "waving path" like a "rectangular" with sinusoid >> curves as borders as the source for the distortion. Then a distorted >> "normal" rectangular would take on this shape, hence the linear borders >> get "waved". This, however, is not implemented in any of the above >> examples. But I think, it would be a very powerful feature. >> >> For sake of implementing, the feature could be restricted to a path with >> four straight lines, but I think, it would hugely diminish the power of >> the idea. >> >> Best, >> Manuel >> >> Dr. Olaf Hoffmann schrieb: >>> Having some experience already with 3D transformations >>> and different projections from 3D to 2D, I'd like to ask some >>> questions or to give some suggestions about this, just to >>> get a personal impression: >>> >>> Maybe it would already help to have some formulas to see, >>> how such transformation can be implemented? >>> >>> If you have it for some examples or even some simulations, >>> how this works this could help. For example PHP-scripts doing >>> the transformation and presenting the result in current SVG, >>> this could be already used to explore the behaviour >>> and possible difficulties and applications ... >>> >>> Especially do this conversions conserve the structure >>> of the path (straight lines are still straight lines or points, >>> cubic beziers are converted just in other cubic beziers >>> just by conversion of points and control points etc) or >>> does it create completely new paths, a viewer has to >>> calculate for each device pixel? >>> I think, with such a simple approach the viewer has >>> not to care in a specific way about the rendering order >>> as this happens for non trivial 3D-2D projections? >>> >>> >> >> > > -- > > -- > Andreas Neumann > Böschacherstrasse 6 > CH-8624 Grüt (Gossau ZH) > Switzerland > Phone: ++41-44-2736668 > Email: a.neumann@carto.net > > Web: http://www.carto.net/neumann/ > SVG Examples: http://www.carto.net/papers/svg/samples/ > SVG.Open: http://www.svgopen.org/ >

Received on Tuesday, 2 September 2008 06:45:34 UTC